«The toolbox bundles a selection of functions to compute Time Domain, Frequency Domain, and nonlinear HRV parameters, along with other additional features designed to support your HRV research:
https://pyhrv.readthedocs.io/en/latest/
developer: Pedro Gomes, PLUX wireless biosignals S.A. («Bitalino»)
pyHRV Citation & Publications:
https://github.com/PGomes92/pyhrv/blob/master/publications.md
Watches with HRV Recording (list needs to be updated)
https://fellrnr.com/wiki/Heart_Rate_Variability#Watches_with_HRV_Recording